After read the Linux user guide (L2.6.35_1.1.0), 'mem' is supported. But you need to do some modification before use it.

2.6 Building Kernel to Support Suspend-To-RAM Mode

In suspend-to-RAM mode, only DRAM is in self-refresh mode and is powered by external circuit; ARM core, on-chip modules, and PLL are off. After entering suspend-to-RAM mode, only power key can resume, then system starts a code boot. To enter suspend-to-RAM, run the following command: